This proposal requests support for the ninth Gordon Research Conference on Three-Dimensional Electron Microscopy of Macromolecules. Electron microscopy occupies a unique position in the biological armamentarium in that it can address questions at the molecular and cellular level that cannot be approached using other structural methods. In recent years, important technical breakthroughs have been made which enable three-dimensional structures to be determined with ever increasing accuracy, and which have opened the way to the study of macromolecular systems under defined physiological conditions. As a result, there are exciting new opportunities for understanding biological mechanisms, interactions between macromolecules and the principles of bio-molecular design. This series of conferences fosters an integrated view of biological complexity by bringing together scientists working at different levels of the structural hierarchy. These meetings serve to define the challenges of the future and to focus a concerted approach to problems in the preparation, imaging and interpretation of biological specimens that range in size from the molecular to the subcellular. The impact of the preceding eight conferences has been such that the 3D EM community has come to regard this Gordon Conference as an event of pivotal importance. The theme of the conference in 2001 is "High Throughput At High Resolution." In organizing this conference, our goal has been to create a dynamic forum for (i) the dissemination of the major progress in the field over the past two years and (ii) identification of the new technical and biological challenges which the field must address in order for 3D EM to become an essential and ubiquitous tool for the solution of cell biological problems. In the spirit of the Gordon Conference, we have chosen a program that represents the frontier of our field. Speakers have been chosen on the basis of the importance of their recent contributions and the potential impact of their particular research approach. Based on past experience, we confidently expect that the 3D EM Gordon Conference will continue to play a central role in defining new technical challenges, and in focusing a concerted approach to the understanding of fundamental biological questions.